A variety of food products containing meat are readily adaptable to replacement of their normal meat constituents with textured vegetable protein. These foods include sauces such as spaghetti sauce, taco sauce, chili mixes and others. Purely thermal sterilization of such products leads to loss in flavor acceptability due to the development in the product of burned and browned flavors, as well as thermal reaction product off-flavors.
The Federal Regulations of the Food and Drug Administration permit canners of foods to acidify their products to a pH of 4.6 or below as an alternative to thermal retort sterilization. By acidification of such products to a pH of 4.6 or below, the products are rendered microbiologically safe if the products are sealed into containers at elevated temperatures, and held for a sufficient time to destroy molds, yeasts, and vegetative bacteria prior to cooling. Most acidified foods are kept at a pH well below 4.6, because above about 4.2, growth of Bacillus coagulans occurs, causing flat sour spoilage of the product. Acidification permits use of less severe processing conditions without sacrificing product safety.
Several processing techniques for acidification are approved by the Food and Drug Administration. These include (1) blanching of the food ingredients in acidified aqueous solutions; (2) immersion of the blanched food in acidified aqueous solutions; (3) direct batch acidification by adding a known amount of an acid solution to a specified amount of food; (4) direct addition of a predetermined amount of acid to individual containers during production; and (5) addition of acid foods to low-acid foods in controlled proportions to conform to specific formulations.
When meat, poultry, or textured protein is a component of acidified foods it acts as a buffer and raises the pH of the product. At a higher pH the growth of bacteria is favored. In addition, the internal pH of pieces of textured protein, meat, or poultry, can have a center pH greater than that of the food product as a whole, thus providing an environment favoring bacterial growth. Therefore, to insure product safety and stability it must be permitted to equilibrate to assure that a low center pH has been achieved. This equilibration time can require several days or weeks depending upon the characteristics of the individual product. A means for minimizing this equilibration time while assuring a safe shelf-stable product is desirable.
U.S. Pat. No. 3,886,296 of Brooks et al., issued May 27, 1975, discloses a hot acid blanching process for canning foods wherein the food particles are blanched with a hot acid solution to a pH of 5.0, submersed totally within a liquid phase having a pH below 4.5, and heat sterilized. The pH of the food is measured on the total product in comminuted form. However, the pH of the center of discrete pieces could be higher. Direct acidification, instead of acid blanching, of meat, poultry or textured protein particles ot a pH well below 5.0 would aid in decreasing the time required to lower the pH throughout the product. Direct acidification would also eliminate the requirement for total liquid coverage of food particles in the final product. However, it has been found that if ground meat or poultry is acidified to below about 4.8 prior to its combination with a liquid or sauce phase the meat becomes discolored and disintegrated. Acid blanching causes destruction of cellular integrity, and meat or poultry becomes soft or mushy in texture. Acidification can also have an adverse effect on textured protein. Acidification of textured protein can cause it to disintegrate by decreasing the functionality of the binder employed. As pH decreases, binding generally decreases. Texture and size of the meat, poultry, or protein pieces is critical to product quality and acceptance. A process for acidification of food products containing significant amounts of textured vegetable protein which rigorously protects product safety, while having a minimal impact on product texture is needed.
U.S. Pat. No. 3,736,148 of Katz, issued May 29, 1973, discloses meat analogs resistant to microbiological spoilage having a pH between 3.0 and 5.4 and a water activity of below 0.95. Katz restricts the water level of the analogs as an aid in preventing the growth of microorganisms. Restriction of water activity limits the optimum texture and flavor which can be achieved. The Katz analogs contain preservatives and texture modifiers such as starches, gums, and the like. Natural products without food additives such as preservatives and texture modifiers are preferred by consumers. It is desirable to have textured protein products which do not contain preservatives and texture modifiers that are microbiologically safe without restriction of the water activity in order to optimize texture and flavor.
As the pH is decreased, textured protein present in food products begins to acquire a sharp, sour, astringent flavor, presumably due to some chemical change in the material at this pH. Thus, acidification can have a detrimental effect on flavor just as purely thermal processing. A process for sterilization of acidified food products containing significant amounts of textured vegetable protein which rigorously protects product safety, while having a minimal impact on product flavor is needed.
A process has now been found for direct acidification of a product containing textured protein. Disintegration of the protein particles is avoided and an optimum texture is provided. No increase in sour flavor occurs despite the decrease in pH. In addition, other beneficial effects of this acidification process are to reduce pH equilibration time for large textured protein or analog pieces, and to reduce fat absorption by the protein during heatsetting. Thus, a microbiologically safe product containing textured protein or analog having a desirable firm texture and acceptable flavor with reduced fat levels can be generated by this acidification process.
It is therefore an object of this invention to provide a shelf-stable acidified textured protein sauce product containing discrete pieces of protein or analog of optimal texture which has a pH of less than 4.6, acceptable flavor, and reduced fat content.
It is a further object of this invention to provide a process which renders a food product having a pH less than 4.6 and containing high levels of textured protein bacteriologically safe and shelf-stable.
It is a further object of this invention to provide a process for minimizing the pH equilibration time required for a textured protein product containing large discrete pieces of protein or analog.
It is a further object of this invention to provide a process for the preparation of an acidified textured protein product with less fat.
It is a further object of this invention to provide a process for the preparation of an acidified textured protein product of optimal texture without disintegration of the protein.
It is a further object of this invention to provide a process for the preparation of an acidified textured protein product of low pH with an acceptable flavor.
These and other objects of the invention will become obvious from the following descriptions and examples.